Amplify: Expo Could not connect to development server

Question

I have a React-Native app, using AWS Amplify that works with Expo when testing using expo start --web, but I am trying to test on my iOS device and get a Could not connect to development server. Error. URL: http://192.168.1.6:19000/node_modules%5Cexpo%5CAppEntry.bundle?platform=ios&dev=true&hot=false&minify=false

EDIT: I have tried starting a blank project, using amplify pull, and then this error occurs:

jest-haste-map: Haste module naming collision: projectamplifyjsc7fc9745PostConfirmation
  The following files share their name; please adjust your hasteImpl:
    * <rootDir>\amplify\#current-cloud-backend\function\projectamplifyjsc7fc9745PostConfirmation\src\package.json
    * <rootDir>\amplify\backend\function\projectamplifyjsc7fc9745PostConfirmation\src\package.json    

Failed to construct transformer:  DuplicateError: Duplicated files or mocks. Please check the console for more info
    at setModule (C:\Users\me\Desktop\project\node_modules\jest-haste-map\build\index.js:620:17)
    at workerReply (C:\Users\me\Desktop\project\node_modules\jest-haste-map\build\index.js:691:9)
    at processTicksAndRejections (internal/process/task_queues.js:93:5)
    at async Promise.all (index 50) {
  mockPath1: 'amplify\\#current-cloud-backend\\function\\projectamplifyjsc7fc9745PostConfirmation\\src\\package.json',
  mockPath2: 'amplify\\backend\\function\\projectamplifyjsc7fc9745PostConfirmation\\src\\package.json'}
Error: Duplicated files or mocks. Please check the console for more info
    at setModule (C:\Users\me\Desktop\project\node_modules\jest-haste-map\build\index.js:620:17)
    at workerReply (C:\Users\me\Desktop\project\node_modules\jest-haste-map\build\index.js:691:9)
    at processTicksAndRejections (internal/process/task_queues.js:93:5)
    at async Promise.all (index 50)
Error: Duplicated files or mocks. Please check the console for more info
    at setModule (C:\Users\me\Desktop\project\node_modules\jest-haste-map\build\index.js:620:17)
    at workerReply (C:\Users\me\Desktop\project\node_modules\jest-haste-map\build\index.js:691:9)
    at processTicksAndRejections (internal/process/task_queues.js:93:5)
    at async Promise.all (index 50)

What is this and how to fix?

score 0 · Accepted Answer · answered Oct 12 '21 at 14:28

This answer comes from someone who had a similar issue with the Amplify API, find it here: Amplify React Native - Duplicate Error using amplify add api

Solution is simple (at least for me, guess it could depend on what amplify services you use).

Amplify creates a copy of your current cloud backend configuration in amplify/#current-cloud-backend/.

You don't need those files to build your app, so you can ignore them in order to get rid of the error.

To do so, you can create a blacklist and add the folder to it. Create a rn-cli.config.js file in the root of your project.

./rn-cli.config.js:
require('metro').createBlacklist;

const blacklist = require('metro-config/src/defaults/blacklist');

module.exports = {   resolver: {
    blacklistRE: blacklist([/#current-cloud-backend\/.*/]),   }, }; ```

See answer given here: https://stackoverflow.com/a/60899723/11255886

Amplify: Expo Could not connect to development server

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